Fan frame and mold for making the same

ABSTRACT

A heat dissipation assembly includes a fan frame ( 11 ), a blade set ( 12 ) rotably mounted in the fan frame, a support member ( 30 ) abutting the fan frame, and a number of fasteners ( 20 ) mounting the fan frame on the support member. The fan frame defines an inner cavity receiving the blade set, a number of circular through apertures ( 18 ) for insertion of the fasteners respectively, and a number of slits ( 19 ) communicating with the through apertures to allow the through apertures to be resiliently expandable. For making the fan frame, a female mold ( 50 ) includes a number of posts ( 56 ) extending therefrom, and a connecting plate ( 58 ) connected between a main part of the female mold and each post.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates generally to cooling fans for use in heat dissipation assemblies for cooling electronic packages, and more particularly to a fan frame of a cooling fan and a mold for making the fan frame.

FIG. 3 illustrates a conventional cooling fan 100 having a frame 101 with an inner cavity, and a blade set 103 rotatably received in the inner cavity. Four through holes 105 are formed at corners of the frame 101 respectively. The through holes 105 allow fasteners such as screws to extend therethrough and engage in another member, such as a fan holder which is secured on a heat sink, thereby mounting the cooling fan 100 on the heat sink. The periphery of the frame 101 adjacent each hole 105 is thinner than adjacent portion of the frame 101, and therefore forms a localized area of high stress also referred to as stress concentration at the thinner portion of the frame 101. When the screw 105 engages in the hole 105, these thinner portions of the frame 101 at the holes 105 are prone to be damaged.

FIG. 4 illustrates a mold for making the frame 101 of the conventional fan 100. The mold comprises a female mold 90 and a male mold 80 inserting into the female mold 90. A gap 70 is formed between the female mold 90 and the male mold 80. The gap 70 has a shape of the frame 101. In molding, molten plastic is injected into the gap 70, and the mold is cooled to freeze the plastic to form the shape of the frame 101.

Referring to FIGS. 5 and 6, in order to form the though holes 105 of the frame 101, four posts 92 are formed on a bottom wall of the female mold 90. Each post 92 is slim, and is connected to the bottom wall of the female mold 90 with only one end of the post 92 joining with the bottom wall of the female mold 90. This configuration will cause stress concentration at a joint area 94. When the post 92 is subject to vibration or shock during transportation of the mold or subject to unexpected radial force during the molding process, the post 92 is very likely to break off from the joint area 94.

For the foregoing reasons, there is a need for a fan frame which has an improved resistance against breakage, and also there is a need for a mold molding the fan frame which has an improved resistance against unexpected shock or force.

SUMMARY OF THE INVENTION

The present invention is directed to cooling fan whose fan frame has an improved resistance to breakage due to stress concentration.

The present invention is also directed to a mold for making the fan frame which has improved resistance against unexpected shock or force.

A cooling fan in according with a preferred embodiment of the present invention comprises a fan frame, a blade set rotably mounted in the fan frame, a support member abutting the fan frame, and a plurality of fasteners mounting the fan frame on the support member. The fan frame defines an inner cavity receiving the blade set, a plurality of circular through apertures for insertion of the fasteners respectively, and a plurality of slits communicating with the through apertures to allow the through apertures to be resiliently expandable.

A mold for make a fan frame according to a preferred embodiment of the present invention comprises a male mold and a female mold cooperatively define a gap resembling the shape of the fan frame therebetween. The female mold comprises a main part having a bottom wall and a plurality of sidewalls extending from the bottom wall. A plurality of posts having a same height extends perpendicularly from the bottom wall. A connecting plate is connected between the main part and each of the posts.

Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiments of the present invention with attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a preferred embodiment of a heat dissipation assembly having a cooling fan embodying features of the present invention;

FIG. 2 is a top, cut view of a mold for the fan frame of FIG. 1;

FIG. 3 is a perspective view of a conventional cooling fan;

FIG. 4 is an assembled, cross-sectional view of a mold for the conventional cooling fan of FIG. 5;

FIG. 5 is a top, cross sectional view of the female mold along line A-A of FIG. 4; and

FIG. 6 is a cross-sectional view of the female mold along line B-B of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, a heat dissipation assembly according to a preferred embodiment of the present invention comprises a support member 30, a cooling fan 10, and a plurality of fasteners such as screws 20 for mounting the cooling fan 10 to the support member 30.

The cooling fan 10 comprises a fan frame 11 defining an inner cavity, and a blade set 12 rotatably received in the inner cavity of the fan frame 11. A plurality of circular apertures 18 is defined in the fan frame 11 around the cavity, for insertion of the screws 20 thereinto respectively. In this exemplificative embodiment, the fan frame 11 has a square outer periphery and the through apertures 18 are arranged at corners of the fan frame 11 respectively. Understandably, the outer periphery of the fan frame 11 can be round or other shapes according to practice. The fan frame 11 at each corner thereof splits so as to make each aperture 18 open outwardly, thereby defining a slit 19 at each of the corners to communicate with both a corresponding aperture 18 and an exterior of the fan frame 11. These slits 19 allow the through apertures 18 to be resiliently expandable.

The support member 30 is an element for mounting the fan frame 11 and varying with situations in which the cooling fan 10 is used. Suppose the cooling fan 10 cooperates with a heat sink to cool an electronic package, the support member 30 is the heat sink if the cooling fan 10 is directly secured to the heat sink. However, if a fan holder is used to retain the cooling fan 10 on the heat sink, the support member 30 is the fan holder. Suppose another situation, the cooling fan 10 is mounted to a wall of a computer enclosure at a venting hole thereof for ventilation of the computer enclosure, the support member is the wall of the computer enclosure.

Referring to FIG. 2, a mold for making the fan frame 11 is shown. FIG. 2 only shows a female mold 50. The female mold 50 comprises a bottom wall 52 and four sidewalls 54 extending perpendicularly from sides of the bottom wall 52 to cooperatively define an inner space therebetween. Four cylindrical posts 56 having a same height extend perpendicularly and upwardly from the bottom wall 52, near the respective corners of the female mold 50. A connecting plate 58 extends in a radial direction from a periphery of each post 56 to a junction of two adjacent sidewalls 54. A junction line of each post 56 and a corresponding connecting plate 58 is parallel to the axis of the post 56. Each connecting plate 58 has a same height with the post 56.

The conventional male mold, such as the male mold 80 shown in FIG. 4, may be adopted to cooperate with the female mold 80 of the present invention to mold the fan frame 11. The male mold 80 is received in the inner space of the female mold 50. A gap resembling the shape of the fan frame is formed between the male mold 80 and the female mold 50. In molding the fan frame 11, molten plastic material is injected into the gap. After the molten plastic solidify to form the fan frame 11, the male mold 80 is withdrawn from the female mold 50. Then the fan frame 11 is removed from the female mold 50.

In the fan frame 11 according to the present invention, the slits 19 allow the fan frame 11 adjacent corresponding apertures 18 to resiliently deform to expand the apertures 18, therefore eliminate the stress concentration phenomena of the fan frame at the apertures 18. In the mold according to the present invention, each post 56 connects to the main part of the female mold 50 not only by its bottom end fixed to the bottom wall 52 of the female mold 50, but also by its periphery fixed to the connecting plate 58 which is connected to the sidewalls 54. This arrangement greatly increases the joining force between the post 56 and the main part of the female mold 50. The post 56 is thus able to withstand greater shock during transportation and radial force during molding process or machining of the post 56 itself.

It is understood that the invention may be embodied in other forms without departing from the spirit thereof. The above-described examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given above. 

1. A heat dissipation assembly comprising: a fan frame defining an inner cavity, a plurality of circular through apertures around the inner cavity, a plurality of slits communicating with the through apertures to allow the through apertures to be resiliently expandable; a blade set rotatably mounted in the inner cavity; a support member supporting the fan frame thereon; and a plurality of fasteners extending through the through apertures respectively and engaging with the support member so as to mount the fan frame on the support member.
 2. The assembly as described in claim 1, wherein the fan frame has a square outer periphery with the through apertures defined at corners thereof respectively.
 3. The assembly as described in claim 1, wherein the slits are in communication with an exterior of the fan frame thereby making the through apertures open outwardly.
 4. The assembly as described in claim 1, wherein the fasteners are screws.
 5. The assembly as described in claim 1, wherein the support member is a fan holder that is secure to a heat sink.
 6. The assembly as described in claim 1, wherein the support member is a heat sink.
 7. The assembly as described in claim 1, wherein the support member is a wall of a computer case.
 8. A mold for making a fan frame, the mold comprising: a male mold; and a female mold comprising a main part having a bottom wall and a plurality of sidewalls extending from the bottom wall to cooperatively define an inner space therebetween for receiving the male mold therein, the male mold and the female mold cooperatively defining a gap resembling the shape of the fan frame therebetween, a plurality of posts having a same height extending perpendicularly from the bottom wall, a connecting plate connected between the main part and each of the posts.
 9. The mold as described in claim 8, wherein the connecting plate has a same height with the post.
 10. The mold as described in claim 9, wherein the connecting plate is connected to a junction of two adjacent sidewalls.
 11. The mold as described in claim 8, wherein the connecting plate is perpendicular to the bottom wall.
 12. A fan for heat dissipation, comprising: a blade set; and a fan frame receiving said blade set so as to keep said blade set operatable therein, said fan frame having a plurality of through apertures disposed around said blade set, each of said through apertures extending through said fan frame to expose to outside of said fan frame at two opposing ends thereof, and at least one slit formed with said each of said through apertures to allow said each of said through apertures communicating with outside of said fan frame from a face of said each of said through apertures other than said two opposing ends.
 13. The fan as described in claim 12, wherein said each of said through apertures is resiliently extendable along a direction perpendicular to an extending direction of said at least one slit. 